Move / Copy File Operations in Java

StackOverflow https://stackoverflow.com/questions/300559

  •  08-07-2019
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Question

Is there a standard Java library that handles common file operations such as moving/copying files/folders?

Was it helpful?

Solution

Here's how to do this with java.nio operations:

public static void copyFile(File sourceFile, File destFile) throws IOException {
    if(!destFile.exists()) {
        destFile.createNewFile();
    }

    FileChannel source = null;
    FileChannel destination = null;
    try {
        source = new FileInputStream(sourceFile).getChannel();
        destination = new FileOutputStream(destFile).getChannel();

        // previous code: destination.transferFrom(source, 0, source.size());
        // to avoid infinite loops, should be:
        long count = 0;
        long size = source.size();              
        while((count += destination.transferFrom(source, count, size-count))<size);
    }
    finally {
        if(source != null) {
            source.close();
        }
        if(destination != null) {
            destination.close();
        }
    }
}

OTHER TIPS

Not yet, but the New NIO (JSR 203) will have support for these common operations.

In the meantime, there are a few things to keep in mind.

File.renameTo generally works only on the same file system volume. I think of this as the equivalent to a "mv" command. Use it if you can, but for general copy and move support, you'll need to have a fallback.

When a rename doesn't work you will need to actually copy the file (deleting the original with File.delete if it's a "move" operation). To do this with the greatest efficiency, use the FileChannel.transferTo or FileChannel.transferFrom methods. The implementation is platform specific, but in general, when copying from one file to another, implementations avoid transporting data back and forth between kernel and user space, yielding a big boost in efficiency.

Check out: http://commons.apache.org/io/

It has copy, and as stated the JDK already has move.

Don't implement your own copy method. There are so many floating out there...

Previous answers seem to be outdated.

Java's File.renameTo() is probably the easiest solution for API 7, and seems to work fine. Be carefull IT DOES NOT THROW EXCEPTIONS, but returns true/false!!!

Note that there seem to be problems with it in previous versions (same as NIO).

If you need to use a previous version, check here.

Here's an example for API7:
        File f1= new File("C:\\Users\\.....\\foo");
        File f2= new File("C:\\Users\\......\\foo.old");
        System.err.println("Result of move:"+f1.renameTo(f2));

Alternatively:

    System.err.println("Move:" +f1.toURI() +"--->>>>"+f2.toURI());
    Path b1=Files.move(f1.toPath(),  f2.toPath(), StandardCopyOption.ATOMIC_MOVE ,StandardCopyOption.REPLACE_EXISTING ););
    System.err.println("Move: RETURNS:"+b1);

Try to use org.apache.commons.io.FileUtils (General file manipulation utilities). Facilities are provided in the following methods:

(1) FileUtils.moveDirectory(File srcDir, File destDir) => Moves a directory.

(2) FileUtils.moveDirectoryToDirectory(File src, File destDir, boolean createDestDir) => Moves a directory to another directory.

(3) FileUtils.moveFile(File srcFile, File destFile) => Moves a file.

(4) FileUtils.moveFileToDirectory(File srcFile, File destDir, boolean createDestDir) => Moves a file to a directory.

(5) FileUtils.moveToDirectory(File src, File destDir, boolean createDestDir) => Moves a file or directory to the destination directory.

It's simple, easy and fast.

Interesting observation: Tried to copy the same file via various java classes and printed time in nano seconds.

Duration using FileOutputStream byte stream: 4 965 078

Duration using BufferedOutputStream: 1 237 206

Duration using (character text Reader: 2 858 875

Duration using BufferedReader(Buffered character text stream: 1 998 005

Duration using (Files NIO copy): 18 351 115

when using Files Nio copy option it took almost 18 times longer!!! Nio is the slowest option to copy files and BufferedOutputStream looks like the fastest. I used the same simple text file for each class.

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